This invention relates to a cement spacer which can be used in a prosthetic cup and to a method of sterilization thereof.
Prosthetic cups adapted to be held in place in a receptive opening in a bone can have an outer surface provided with one or more projecting cement spacers to space the outer surface of the cup away from the receptive opening in which it is placed. The resulting gap around the cup provided by the spacer or spacers enables the thickness of cement to be controlled. Spacers of this type are well known for this purpose such as shown in U.S. Pat. Nos. 4,563,778 and 4,955,325.
The spacers can be provided in many ways but are often formed as projections on the outer surface of, for example, a prosthetic hip cup.
Products for use in surgery require sterilization and cups made from, for example, polyethylene can be sterilized with a gas plasma sterilization process. With this process the gas has to be present on all the surfaces of the product to sterilize it. There can be problems with sterilizing polyethylene cups at a level of the cement spacers. If the spacers are, for example, separate items pressed into openings in the outer surface of the cup the gas cannot penetrate behind the spacers and on the sides of any location portions which locate the spacers in the openings. Spacers of this type can, for example, be pressed into drilled holes of a diameter slightly less than location portions so that the results is an interference fit and the spacers are held rigidly in position. As mentioned above, however, this causes problems with sterilization when using a gas plasma sterilization process.